Generally, food packagers put more food in a package than is stated on the label in order to insure that the majority of containers contain at least the stated label weight. This is so, because of the relatively strict regulation of the food industry with respect to labeling practices. The excess of food in a package over and above that stated on the label is termed "give-away," Therefore, the consumer pays for a package having the stated label weight, but in reality normally receives somewhat more food.
Normally, the amount of give-away in a typical food package is nominal in terms of percentage of the label weight. It is to be appreciated, however, that over a period of a year the cost of such give-away for a given food producer is substantial. Therefore, the producer makes every effort to minimize the amount of give-away while maintaining a required percent of packages at a weight equal to or above the label weight within the packaging regulations of the government.
For sliced food packages, such as cheese and meat products, a rotating or reciprocating blade is used to slice cheese or meat having different forms such as loaves, bellies, hams, slabs of bacon and the like. After a predetermined number or all of the slices have been cut, the package is weighed and compared against a preset standard. An adjustment is made to the feed rate before cutting following slices. It is seen that the final weight of the sliced food package, for a given number of slices, is determined by the thickness of an individual slice, which is controlled by the rate at which the food is fed to the slicing mechanism.
Generally, in such a slicing system, the idea is to produce a package having a desired batch weight with substantially uniform slice thickness. This is difficult to achieve when slicing from a non-uniform or non-homogeneous loaf which varies significantly along its length in either density or dimension. Such non-uniform or non-homogeneous loaves, for example, are slabs of bacon, swiss cheese or the like. Since uniformity in slice thickness is more readily apparent to the consumer than uniformity of slice weight, unacceptable batches may be produced if the control system is set to achieve substantially uniform slice weight for a fixed number of slices.
In a control system for solid slicing as set forth in U.S. Pat. No. 3,508,591 of Johnson et al, which is assigned to the assignee of the present invention, a system is set forth for obtaining a preselected fixed number of slices of substantially uniform weight from a solid to provide a batch having a desired batch weight. The partial batch weight is measured after each slice is added and based on the number of slices and partial batch weight a predicted terminal error signal is calculated. The predicted terminal error signal is employed in one of a number of control algorithms and control effected to vary the feed rate of the solid into the slicing mechanism such that the thickness of each slice is regulated to obtain uniform slice weight, thereby minimizing deviation from the desired batch weight. Accordingly, there may be little uniformity in slice thickness when a non-uniform or non-homogeneous solid is sliced since an individual slice weight is determined by the density of the solid in the area being sliced.
According to the present invention, rather than trying to obtain a preselected fixed number of slices of substantially uniform slice weight from a solid to provide a desired batch weight, as is done in Johnson et al, the number of slices N for a given package is variable between high and low limits and a terminal value for N is estimated or predicted to obtain slices of uniform thickness for a desired batch weight. A terminal error signal for controlling the slicing mechanism is calculated based on the estimated value of N resulting in a package of uniform slice thickness and having a weight substantially equal to the desired batch weight.